Nanocomposite materials, that is, materials having homogenously dispersed inorganic nanoparticles in an organic binder, have been used as protective transparent coatings for various applications. Such materials may have improved abrasion resistance and/or optical properties (e.g., refractive index) as compared to coatings of the corresponding organic binder not having inorganic nanoparticles dispersed therein.
Nanocomposite materials containing various inorganic nanoparticles, such as titania (i.e., titanium dioxide) nanoparticles, have been described. Titania occurs in at least three crystal forms: anatase, brookite, and rutile. Of these, the rutile form has the greatest density, hardness, and refractive index.
Major problems with preparing titanium oxide sols, and particularly titanium oxide sols having the rutile crystalline phase may include: long process times, the need to use additional stabilizing counterions (e.g., chloride, nitrate, etc.) that must be laboriously removed prior to use in applications such as organic protective films, extreme pH values, and/or limited stability.
It would be desirable to have quick and easy methods for preparing stable colloidal dispersions of inorganic particles containing titanium, wherein the particles have properties at least comparable to the rutile form of titania. It would also be desirable to homogeneously incorporate such particles into an organic binder to provide high index of refraction abrasion resistant coatings.